The United States Code explicitly limits the total number of general officers that may be on active duty at any given time. The total number of active duty general officers is capped at 231 for the Army, 198 for the Air Force, and 61 for the Marine Corps.[1] Some of these slots are reserved or finitely set by statute. For example the Deputy Judge Advocate General of the Army[2] is a major general in the Army; the same rank is held by the Deputy Judge Advocate General of the Air Force;[3] the Army's Chief of Engineers[4] is also a major general.

To be promoted to the permanent grade of major general, officers who are eligible for promotion to this rank are screened by an in-service promotion board comprising other general officers from their branch of service.[5] This promotion board then generates a list of officers it recommends for promotion to general rank.[6] This list is then sent to the service secretary and the Joint Chiefs of Staff for review before it can be sent to the President, through the Secretary of Defense for consideration.[7] The President nominates officers to be promoted from this list with the advice of the Secretary of Defense, the service secretary, and if applicable, the service's chief of staff or commandant.[8] The President may nominate any eligible officer who is not on the recommended list if it serves in the interest of the nation, but this is uncommon. The Senate must then confirm the nominee by a majority vote before the officer can be promoted. Once confirmed, the nominee is promoted to that rank on assuming a position of office that requires an officer to hold the rank. For positions of office that are reserved by statute, the President nominates an officer for appointment to fill that position. For all three uniformed services, because grade of major general is a permanent rank, the nominee may still be screened by an in-service promotion board to add their input on the nominee before the nomination can be sent to the Senate for approval. Since the grade of major general is permanent, the rank does not expire when the officer vacates a two-star position. Tour length varies depending on the position, by statute, and/or when the officer receives a new assignment but the average tour length per two-star billet is two to four years.

In the Army, Major Generals (MG) typically serve as division commanders (e.g., infantry divisions, cavalry division, etc.), training center commanders, joint task force commanders, deputy commanding generals to 3-star and 4-star commands, senior directors on Army and joint staffs, and, in the case of the Army National Guard, as The Adjutant General (TAG) for their state, commonwealth or territory.

In the Air Force, Major Generals (Maj Gen) typically serve as Numbered Air Force commanders, vice commanders of 3-star commands, joint task force commanders, warfare center, training center, weapons center, or logistics center commanders, or senior directors on Air Force and joint staffs. In the case of the Air National Guard, they may also serve as The Adjutant General (TAG) for their state, commonwealth or territory.

Other than voluntary retirement, statute sets a number of mandates for retirement. All major generals must retire after five years in grade or 35 years of service, whichever is later, unless appointed for promotion or reappointed to grade to serve longer.[9] Otherwise all general officers must retire the month after their 64th birthday.[10] However, the Secretary of Defense can defer a general officer's retirement until the officer's 66th birthday and the President can defer it until the officer's 68th birthday. Because there are a finite number of General Officer positions, one officer must retire before another can be promoted. As a result, General Officers and, in the case of the U.S. Navy and U.S. Coast Guard, Flag Officers typically retire well in advance of the statutory age and service limits, so as not to impede the upward career mobility of their juniors.

The rank of Major General was abolished in the U.S. Army by the Act of March 16, 1802,[11] and restored by the Act of January 11, 1812,[12] as preparations were being made for the War of 1812. Major General has been a rank in the U.S. Army ever since.

The position of Major General Commanding the Army was entitled to wear three stars according to General Order No. 6 of March 13, 1861.[14] When Ulysses S. Grant was appointed lieutenant general on March 9, 1864,[15] and took command of the Union forces, he used the three-star insignia formerly assigned to that position.

The Confederate States Army maintained a similar rank of major general, usually associated with the command of a division, while lieutenant generals often commanded corps and full generals led armies as a general convention.

There was no Major General in the U.S. Marine Corps until CommandantCharles Heywood was specially promoted by Act of Congress in July 1902. From his retirement on October 3, 1903, Brigadier General was again the highest rank in the Marine Corps until May 21, 1908, when the office of Commandant was raised to the rank of Major General. It remained the highest rank in the Marine Corps until January 20, 1942, when the office of Commandant was raised to the rank of Lieutenant General.

[1]No universal insignia for officer candidate rank; Navy candidate insignia shown[2]Unofficial 1945 proposal for General of the Armies insignia; John J. Pershing's GAS insignia: ; George Dewey's AN insignia: [3]Rank used for specific officers during World War II and Korea only, not permanent addition to rank structure[4]Grade is authorized by the U.S. Code for use but has not been created[5]Grade has never been created or authorized